ABACK - The sail filling on the wrong side in the case of a square rigger may cause the ship to back up.


ABAFT - Toward the rear (stern) of the boat. Behind


ABEAM - At right angles to the keel of the boat, but not on the boat


ABOARD - On or within the boat


ABOVE BOARD - Above decks, therefore, meaning to be out in the open, visible to all; honest, straight forward, etc.


ABOUT - on the other tack


ABOVE DECK  - On the deck (not over it - see ALOFT)


ABREAST - Side by side; by the side of.


ABYSS - That volume of ocean lying below 300 fathoms from surface


ADMEASURE - Formal measurement of a boat for documentation


ADMIRALTY LAW - The "law of the sea."


ADRIFT - Floating free with the currents and tide, not under control


ADVECTION – The transference of heat or cold by the horizontal movement of a mass of air

AFT - Toward the stern of the boat


AFTER BOW SPRING LINE - A mooring line fixed to the bow of the boat and leading aft where it is attached to the dock. This prevents the boat from moving forward in its berth. Its opposite, the forward quarter spring line, is used to keep the boat from moving aft in its berth


AFTERCABIN - In a ship with multiple cabins the cabin closest to the stern


AFTERMAST - In a sailing ship carrying multiple masts,  the mast set closest to the stern.  Also called the mizzenmast in a three-masted sailing vessel.


AFTERMOST - The farthest aft


AGAINST THE SUN – An Anti-clockwise circular motion. Left-handed ropes are coiled against the sun


AGROUND - Touching or fast to the bottom


AHEAD - In a forward direction


AIDS TO NAVIGATION - Artificial objects used to supplement natural landmarks in indicating safe and unsafe waters.  Any fixed object that a navigator may use to find his position, such as permanent land or sea markers, buoys, radio beacons, and lighthouses.


AIR DRAFT - This is the height of a vessel above the water level; including any cargo or mast's. (See also Draft & Bridge hole)


ALEE - Away from the direction of the wind. Opposite of windward


ALTAR - Step in a dry dock


ALONGSIDE - Close beside a ship, wharf or jetty.

ALOFT - Above the deck of the boat


AHOY - seaman's call to attract attention


AMAS - The outboard hulls of a trimaran


AMERICA'S CUP -The America’s Cup, dating from 1851, is the oldest trophy in is considered yacht racing’s Holy Grail


AMIDSHIPS - In or toward the center of the boat


ANCHOR - Any of a number of heavy, hook-shaped devices that is dropped over the side of the boat on the end of a length of rope and/or chain, and which is designed to hold a vessel securely in place until (a) the wind exceeds 2 knots, (b) the owner and crew depart, or (c) 3 a.m.


ANCHORAGE - A sheltered place or area where a boat can anchor


ANCHOR BALL - A black ball visible in all direction display in the forward part of a vessel at anchor


ANCHOR BEND - A type of knot used to fasten an anchor to its line


ANCHOR CHAIN - A chain attached to the anchor. The chain acts partially as a weight to keep the anchor lying next to the ground so that it can dig in better


ANCHOR ICE - Ice, of any form, that is aground in the sea


ANCHOR LIGHT - A white light visible in all direction display in the forward part of a vessel at anchor


ANCHOR LOCKER -Storage space used for the anchor rode and anchor.


ANCHOR WATCH - A member or members of the crew that keep watch and check the drift of ship.


ANCHOR WINDLASS - A windlass used to assist when raising the anchor


ANEMOMETER - A device that measures wind velocity


ANGLE OF CUT – The smaller angle at which two lines of position on a chart intersect


AP – See Assumed Position


APEAK - Said of an anchor when its cable is taut and vertical.


APPARENT WIND – The direction of the wind as it appears on board.  It differs from the true direction due to the vessel’s motion


ARCH - A curved architectural structure used to support suspended weight. In Great Lakes wooden shipbuilding, a wide iron- or steel-fastened strap down each side of a ship, usually fastened low in the bow and stern and rising to the level of the upper deck amidships provides longitudinal support to the hull


ARCH BOARD - An arch-shaped nameboard fastened to the stern of a ship, displaying the vessel's name and home port.


ARIES – In navigation, the position of the Sun in the sky at the vernal equinox, i.e. at the moment when the Sun is on the celestial equator in the spring


ARM – The part of an anchor extending outward from the crown and terminating at the fluke.


ASH BREEZE – Oar power


ASPECT RATIO - The height of a sail or luff length in relation to its width.


ASSUMED POSITION – Estimated position given in Latitude and Longitude, used to calculate the Local Hour Angle (LHA) of a celestial body


ASTERN - In back of the boat, opposite of ahead.


ATHWART - Across. Transversely.


ATHWARTSHIPS - At right angles to the centerline of the boat; rowboat seats are generally athwart ships.


A-TRIP - Said of anchor immediately it is broken out of the ground.


AUXILIARY - A second method of propelling a vessel. On a sailboat this could be a engine.


AVAST! - The command to stop, or cease, in any operation.


AWASH - Water washing over.


AWEIGH - To raise an anchor off the bottom. The position of anchor as it is raised clear of the bottom.